ASTRONOMY, PROGEESS OP, IN 1891. 



63 



at I'olsdam of tin- spectra of Meta Auriga 



and of Xrt a I'r.-ii- Majoris, and, in the case of 



tin- furint-r, finds the doubling of the lines well 



d mi many of th.i-e taken from Nov. 14. 



nwanl. No particular attention was paid 



t.. tliis fact at tin- time, ami hence one of the 



t discoveries of modem times was then 



ed. 



Change ' tho Motion of Sirius. For sev- 

 eral \ears the motion of this star (the Doe Star) 

 n one of recession, at one epoch it having 

 ii the rate of 20 miles a second, but lately 

 it has (.hanged to one of approach, with a speed., 

 IIMJ; to Prof. Vogel, of nearly two miles a 

 srcond, the spectra of iron and of hydrogen 

 jjivintf 1 !'< and 1'73 mile respectively. The re- 

 ! of its motion is doubtless due, it being a 

 liinary double, to a change in its orbital motion. 

 As it revolves around the center of gravity of the 

 system, its direction of motion will always bo 

 changing. Resides its orbital motion, it has also 

 one .'.f translation through space. 



The companion of this star, which for many 



h:is been visible in telescopes of medium 



M/.e. is now beyond the capacity of even the Lick 



pe, with a power of 3,300. Heretofore 



Mr. Burnham has expressed the opinion that he 



would be able to follow it during its peri-astral 



passage, but he now thinks that it will not be 



again seen for several years Its present distance 



is less than 4'0". 



Jupiter's Satellites. On Sept. 8, 1890, 

 Prof. Barnard observed that the first satellite, 

 while crossing the disk of Jupiter, appeared 

 double. It was thus seen also by Mr. Burnham, 

 the distinguished observer of double stars, and 

 he docs not hesitate to say that it appeared as 

 perfectly duplex as any double star he had ever 

 seen. The observation was made with the 12- 

 inch telescope at the Lick Observatory. Its du- 

 plicity was viewed with different powers, so that 

 no deception could be ascribed to the eye-pieces 

 employed. The observation was strange and 

 unneard-of, and can not fail soon to be confirmed 

 or disproved. If not double, the only possible 

 explanation of the phenomenon is that the satel- 

 lite is surrounded by a luminous belt parallel to 

 those of the planet. 



Rotation of Mercury and Tenus. The sup- 

 posed discovery of Schiaparelli, that these planets 

 complete one rotation only while making a revo- 

 lution round the sun, is not accepted by all as- 

 tronomers. Apropos to this, MM. Niestenr and 

 Stuyvacrt, of the Royal Observatory of Belgium, 

 who have studied Venus for ten years, have con- 

 cluded that Cassini's period of the rotation of 

 that planet (twenty-three hours) is correct. 



Nebulae. The quest for nebulae is now sys- 

 tematically prosecuted by only five astronomers, 

 viz. : Bigourdan, of France ; Denning, of Eng- 

 land ; Barnard, of the Lick Observatory ; Stone, 

 of the Observatory of the University of Virginia; 

 and Swift, of the Warner Observatory. This 

 field of work is not now popular, because large 

 telescopes are required to achieve success, inas- 

 much as all of Sir William Herschel's Class I 

 and II, and nearly all so faint as his Class III, 

 have been discovered either by him or his suc- 

 cessors, predecessors of the present searchers for 

 these bodies. The places and magnitudes, with 

 descriptive remarks of all known down to 1888, 



may be found in Dr. Drover's New General Cata- 

 logue, published by the Royal Astronomical So- 

 ciety of England as Vol. XLIX, Part I, of its 

 M.-moirs." 



I'rof. Barnard has recently discovered A new 

 Merorxs nebula in the Pleiades. The old one, 

 found several years ago by Tempel, has, from its 

 supposed variab n the cause of much 



discussion among astronomers, many of whom 

 doubted even its existence. While easily seen 

 with glasses as small as 3 inches, it is invisible 

 in large telescopes, which anomaly is explained 

 by the fact that small telescopes, having large 

 fields of view, give the benefit of contrast with a 

 dark sky, which the contracted fields of great in- 

 struments do not afford. For this reason the 

 tail of Donati's comet could be followed farther 

 bv the naked eye than with the largest telescope. 

 This is true also of the auroral streamers and of 

 the zodiacal light. 



Since the publication of his ninth catalogue, 

 Dr. Swift has added 57 to his previous number 

 of newly discovered nebulae. 



M. Bigourdan, assistant to the Paris Observa- 

 tory, calls attention to the supposed variability 

 of the nebula (New General Catalogue, 1186) 

 situated near the variable star Algol. It was 

 discovered by Sir William Herschel in 1785, and 

 in 1831 observed by Sir John Herschel, since 

 which time there is no record of its having been 

 seen until lately, though searched for. 



Mr. Burnham has examined the vicinity of 

 Hind's variable nebula in Taurus, and found, 

 with the 36-inch telescope of the Lick Observa- 

 tory, a very small, condensed nebula surround- 

 ing the double star T Tauri. But Mr. Roberts 

 has photographed the region, and the plate 

 showed no nebula, nor nebulous star, nor any 

 nebulosity, though the exposure was three hours 

 long. In this instance photography has increased 

 rather than diminished the mystery attaching to 

 the body. It may be that the nebula is deficient 

 in violet rays, and therefore non-photograph- 

 able. Are there not two nebulae here, one being 

 Hind's variable, seen by Otto Struve, D'Arrest, 

 Tempel, and others, and the other that seen by 

 Mr. Burnham, as above f 



For several years Isaac Roberts has made 

 photographic study of the Andromeda nebula, 

 out the majority of his plates, even as late as 

 October, 1890, do not show any trace of a stellar 

 nucleus, while others secured in November and 

 December represent the nucleus as distinctly 

 stellar. He is therefore of the opinion that 

 the nucleus is variable, though further experi- 

 ments may be necessary to corroborate this. 

 The sudden appearance and disappearance in 

 1885 of a star near the center of the nebula lends 

 additional confirmation to the theory of the va- 

 riableness of at least portions of the central part 

 of this interesting nebula, which the spectro- 

 scope declares to be a cluster on a scale of vast- 

 ness equaling, perhaps surpassing, our Milky 

 Way, the shape of which it greatly resembles. 



Meteors. The Perseid meteors which belong 

 to the meteoric shower of Aug. 10 were this year 

 more numerous than has been observed since 

 1871. As seen at the Warner Observatory, and 

 at several widely separated places both in this 

 country and in Europe, the number was so great 

 as to attract general attention. Unlike the 14th 



